The boring or re-boring of holes to tight tolerances in various metals, as when initially forming a cylinder bore or repairing a cylinder bore which has been damaged for some reason, is a common machining problem in the art and can be difficult.
A typical method for boring a hole to a set of required dimensions is to first bore or ream out an opening to an initial diameter which is close to but slightly smaller than the final bore diameter, and to lesser tolerances, with the initial opening then being honed and finished to a final bore diameter with the desired tolerances by use of a honing tool. Such finishing hones for bores are well known in the art and typically include, for example, a number of finishing or grinding surfaces or stones supported on a frame which permits adjustment, in the radial direction, of the diameter of the grinding stones so that the grinding stones can be located against and grind bores having different diameters.
In the case of repairing a damaged bore, for example, the typical repair process will first comprising filling the damaged portion of the bore with a sufficient amount of a desired weld material such that the portion of the bore filled with the weld material has a diameter which is somewhat less than the diameter of the original, undamaged bore. This filling step of the process is typically performed by a conventional bore repair welding device, which is well known in the art, wherein a radially adjustable welding tip is inserted into the damaged area of the bore and rotated to deposit the weld material circumferentially along the damaged inner surface of the bore. Once a sufficient amount of the weld material is deposited, the conventional bore repair welding device is removed and a boring finishing device, such as a cutter mounted on a drill, is inserted within the bore and rotated to order to shave, cut and/or remove excess weld material and eventually achieve a desired bore diameter. In certain instances, the dimensional and alignment accuracies that can be obtained with the cutter are sufficient to meet necessary requirements, and the process is completed solely by use of the rotating cutter.
Many other instances, however, require greater dimensional and alignment accuracies for the bore. In such cases, the cutter merely cuts the bore so that the interior diameter of the bore is sufficiently close to but slightly less than the desired final diameter for the bore. Thereafter, a honing tool is used to hone the diameter and alignment of the bore to the desired final dimensions and tolerances, such as to finish the bore to a desired diameter having a tolerance, for example, of ±0.0005 of an inch or less.
The above processes present a number of problems such as boring tool deflection, bearing play, tool wear, variable hardness in the material, and adjusting the boring tool to a proper radial alignment and dimensions. Further, manual physical manipulation of a conventional bore honing tool, during use, is often cumbersome. These problems tend to be somewhat lessened if the bore being finished has a relative small diameter and length, and such bores are often finished with a stationary hone. That is, a hone which may be clamped or held in a completely stationary position.
The above noted problems, however, become much more significant if the bore is relatively large or relatively long or if the workpiece being finished is relatively large or bulky because such situations typically require a relatively large and heavy boring tool and a corresponding heavy duty motor, such as a large portable drill, to adequately drive the boring tool at a desired rotational speed and with sufficient torque. The honing tools are often designed to be portable because they are often necessary, or at least preferable, when repairing a bore on site. As a result, the honing tool and the motor are typically supported and manipulated directly by the operator, as is conventional in the art. However, because of the weight, the size and the power requirements of the honing tool and the associated drive motor, it is often difficult for an operator to support and manipulate the honing tool and drive motor. These factors result in difficulties in meeting the required bore dimensional and alignment tolerances, significantly increase the time required to complete a honing process, lead to operator fatigue and may possibly create a safety issue which could lead to damage to the honing tool or injury to the operator.
For example, the concentration and physical effort required of the operator just to support and manipulate the honing tool and the drive motor makes it difficult for the operator to notice relatively small changes in the rotational speed and/or the axial position of the honing tool, even though such changes are often indicative of the axial force required to feed or withdraw the tool, such as in compensating for variations in the material hardness or thickness. In addition, portable hones often require a significant amount of axial movement and thus the honing tool is often connected to the drive motor via a drive shaft and a universal joint. This, in turn, leads to an increased risk that the tool can be pulled out of or otherwise be inadvertently removed from the bore during the honing process due to operator error from fatigue or the physical effort required to manipulate the tool, resulting in the hone deflecting radially and swinging around in an uncontrolled fashion.
It will be appreciated that these problems are increased significantly when honing a vertically extending bore since the operator is also then required not only to support the weight of the tool and the motor but also to apply force to the tool and the motor in an upward and downward manner, often in a cramped position.
The present invention addresses these and other related problems associated with the prior art devices and techniques for repairing and finishing a damaged bore.